1. Field of the Invention
The present invention relates to heat and mass transfer enhancement. More particularly, the present invention relates to flow valves for heat and mass transfer enhancement, with anticipated applications in manufacturing, materials processing, electronics cooling, and related industries.
2. General Background of the Invention
Pulsed flows can enhance heat and mass transfer. The reasons are (a) pulsed flows increase mixing and turbulence within the fluid stream, (b) pulsed flows can induce secondary flow structures such as vortex rings that form on the outside of the core of the fluid jet; (c) pulsed flows can result in cyclic formation of boundary layers resulting in thinner time-averaged boundary layers and hence increased driving potential for heat/mass transfer. Reason (a) above also helps to make the heat transfer more spatially uniform along the heat transfer surface. Thus, while steady impinging jets exhibit highly concentrated regions of heat/mass transfer, pulsed jets can provide for more uniform cooling/heating/drying of products (can avoid the "streaking" common in impingement drying processes). Frequency of pulsations is a variable known to influence heat and mass transfer enhancement, with higher frequencies generally producing more enhancement. The duty cycle is a new heat transfer design parameter introduced in this patent. Duty cycle is here defined as the ratio of the flow "on" time to total cycle time.
Attached are papers authored or co-authored by at least one of the inventors of the present invention which include more information about pulsed flows. Papers of interest include:
Eibeck, P. A.; J. O. Keller; T. T. Bramlette; and D. J. Sailor (1993). "Pulse Combustion: Impinging Jet Heat Transfer Enhancement", Combustion Science and Technology, 94, (N1-6), 147-165;
Sailor, D. J. and B. K. Patil (1996). "Variable Duty Cycle Experiments in Pulsed-Impingement Heat Transfer", Proceedings of the National Heat Transfer Conference, HTD-Vol. 330 (8), pp.37-42;
Barattini, V. and D. J. Sailor (1997). "Pulsed Impingement Heat Transfer Enhancement Between an Air Jet and a Heated Surface," Presented at the 1997 ASEE/GSW Annual Conference, Houston, March;
Sailor, D. J. (Jan. 5, 1998) "Innovative Solutions to High Heat and Mass Flux Requirements in Industrial Manufacturing and Drying Processes".
Rohli, D. J., and D. J. Sailor (1998). "Design and Implementation of a Pulsatile Flow Valve for Industrial Heat and Mass Transfer Applications," presented at the 1998 ASEE/GSW Annual Conference, New Orleans, March, pp. 515-518.
U.S. Pat. No. 3,937,252 to Ishida discloses pulses created by rotating sleeve--multiple pulses and phases, but no discussion of duty cycle--applications in generating pulse signals as a function of flow rate.
U.S. Pat. No. 4,802,508 to Styles et al. discloses a lavage system which creates pulsation by diverting the flow alternately through one of two different exit ports, unlike the present system which produces a single pulsed jet without discarding any fluid during the "off" portion of flow. Their system also delivers a "substantially sinusoidal varying pattern of pressure and flow . . ." The present system allows for careful control of the "duty cycle" of the flow profile.
U.S. Pat. No. 4,881,574 to Olson et al. discloses an air pulser for use with a solvent extraction pulse column. This design appears to charge a cavity with pressurized air and then discharge it in a periodic fashion. The physical mechanism is distinctly different from the present approach and the envisioned application is distinctly different.
U.S. Pat. No. 4,649,955 to Otto et al. discloses a distinctly different mechanical concept--plasma physics and laser applications.
U.S. Pat. No. 4,986,307 to Hardee discloses a rotary pneumatic valve, with applications for high-frequency pneumatic switching situations.
U.S. Pat. No. 5,148,946 to Mizuta et al. discloses delivery of predetermined amounts of fluids.
U.S. Pat. No. 4,546,795 to Okamoto et al. discloses a solenoid valve and discusses `pulse width`--a concept similar to duty cycle--(but for purposes of minimizing "collision between valve and valve seat"). Frequency limits of solenoid valves are generally around 50 Hz--the mechanical valve of the present invention can be operated at much higher frequencies, and thus take advantage of the associated heat/mass transfer benefits of high frequencies.
Offenlegungsschrift 29 16 085 (West Germany 1979) discloses a slide valve.
All U.S. Patents and other references mentioned herein are incorporated herein by reference.